Communication system, key managing/distributing server, terminal apparatus, and data communication method used therefor, and program

Abstract

To provide a mobile communication system that can prevent unauthorized use of an encryption key otherwise caused by loss thereof and that can securely perform a direct communication between terminals using the encryption key. A portable terminal apparatus 1-1 transmits a P2P communication trigger to a portable terminal apparatus 1-n through a key managing/distributing server 3. In response to the transmission/reception of the trigger, the portable terminal apparatuses 1-1 and 1-n establish IPsec data sessions with the key managing/distributing server 3 through a SIP server 2 and a secret key is distributed per communication to the portable terminal apparatuses 1-1 and 1-n from the key managing/distributing server 3. The portable terminal apparatuses 1-1 and 1-n establish an IPsec data session therebetween using the secret key, thereby performing a P2P communication. The key managing/distributing server 3 performs key delivery control for switching to the session and establishing the session, with respect to the portable terminal apparatuses 1-1 and 1-n.

Description

TECHNICAL FIELD[0001]This invention relates to a communication system, a key managing / distributing server, a terminal apparatus, a data communication method used therefor, and a program thereof and, in particular, relates to a method of performing a data communication by securely obtaining a dynamically generated encryption key.BACKGROUND ART[0002]In recent years, for portable terminal apparatuses such as portable telephones, following the increasing multifunctionality thereof, a method has been proposed that directly connects between portable terminal apparatuses by short-range wireless communication or the like to perform a data communication therebetween, in addition to wireless communication through a wireless base station. Such a conventional technique is described, for example, in Unexamined Patent Publication No. 2003-087267.[0003]In that event, in the case of connecting the portable terminals by P2P (Peer to Peer: direct communication between terminals) communication (includ...

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Benefits of technology

[0035]Accordingly, in the communication system of this invention, with the terminal apparatuses each including a SIP module, the terminal apparatus on the sending side transmits a data communication start trigger to the terminal apparatus on the receiving side through the SIP server and the key managing/distributing server, thereby enabling the terminal apparatus on the receiving side to receive this trigger in real time.

[0036]With the trigger when the terminal apparatus on the sending side and the terminal apparatus on the receiving side both transmit and receive the data communication start trigger, the terminal apparatuses perform again the location information registration process with respect to the SIP server and, simultaneously, establish signaling sessions between them and the SIP server using the IPsec. By this operation, in the communication system of this invention, the establishing time of the IPsec sessions between the SIP server and the portable terminal apparatuses and the number of the IPsec session establishing terminal apparatuses can be reduced and thus the network load and the server load can be reduced. By performing the signaling on these IPsec sessions, encryption of user information and data necessary for the signaling is performed, thus enabling secure communication.

[0037]Exchange of a secret key for use in P2P data communication between the terminal apparatus on the sending side and the termin

Problems solved by technology

Note, however, that the P2P communication by the short-range wireless communication cannot be realized when the terminal apparatuses are remote from each other.

In the foregoing conventional data communication method, there is a problem that publishing one's own secret key results in that the secret key is possessed by a plurality of persons and, therefore, there is a possibility of unauthorized use thereof.

Further, when the public key cryptosystem is used, complicated encryption and decryption processes are required, which is thus not suitable for processing in a small-scale terminal such as a portable terminal apparatus.

Further, having a plurality of secret keys for

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